1. Field of the Invention:
This invention relates to a printer paper feed apparatus having a single-form feeding function and a continuous-form feeding function. More particularly, the invention relates to a paper feed apparatus well-suited for application to a printer of the type which employs a so-called "push-feed method" wherein a pin tractor mechanism for feeding the abovementioned continuous forms is situated upstream of a platen in terms of the paper feed direction.
2. Description of the Prior Art:
Printers well-known in the art have a friction paper feed mechanism for feeding single forms by a platen and driven pressure rollers, and a pin tractor mechanism for feeding continuous forms.
These printers include ones in which feed is accomplished by employing a so-called "push-feed method" wherein the pin tractor mechanism is located upstream of the platen in the paper feed direction. In comparison with a so-called "pull-feed method" in which the pin tractor mechanism is situated downstream of the platen in terms of paper feed, adopting the push-feed method is advantageous in that a smaller blank portion or "dead space" is required at the leading edge of the continuous forms.
Generally, in a printer having the abovementioned friction paper feed mechanism for single forms and pin tractor mechanism for continuous forms, a single motor is used as the driving source for both mechanisms and it is arranged so that the platen and a tractor driver shaft in the pin tractor mechanism are rotated synchronously at all times. Consequently, when single forms are used, it is required to remove the continuous forms from the pin tractor mechanism. Then, when it is desired to use the continuous forms again, these forms must be reloaded on the pin tractor mechanism. However, as is widely known in the art, engaging the pins of the pin tractor mechanism with the perforations on both side edges of the continuous forms is a fairly troublesome and laborious task for the operator to perform.
However, if an arrangement is adopted in which the rotating force is cut off from the pin tractor mechanism when the single forms are used in the aforementioned printer which feeds the continuous forms by the push-feed method, then this will make it possible to maintain the leading edge portion of the continuous forms in engagement with the pins of the pin tractor mechanism even when the apparatus is used to feed the single forms. Accordingly, it has been contemplated to provide clutch means in the rotation transmission system between the abovementioned paper feed motor and the tractor drive shaft of the pin tractor mechanism, and adopt an arrangement in which the clutch means is operated by hand using a manual operation lever so that the transmission of rotating force to the pin tractor mechanism can be cut off when the single forms are used. However, in a case where the operating lever for clutch control is provided, it is essential that the operator manipulate the lever properly and without fail. More specifically, if the operator inserts a single form into the printer without selecting the single form mode by the operating lever in a state where the leading edge of the continuous forms has been left mated with the pins of the pin tractor mechanism, both the single form and the continuous forms will be fed at the same time.